The present disclosure relates to thermally actuated flow control valves. More particularly, the present disclosure relates to valves including wax-filled actuators employed to control the flow of fluid in automatic transmissions or other heat producing systems.
The use of wax-filled actuators or wax motors in automotive systems is well known. Wax actuators typically utilized in automotive systems are employed to regulate the flow of engine fluids and prevent overheating. Such actuators are designed to open or close in response to a predetermined change in temperature. Wax-filled actuators are reliable temperature-sensitive actuators that require no external energy, such as electricity, control signals, or externally applied actuation force, such as a cable or lever.
Automotive automatic transmissions may utilize a manifold having inlet and outlet fluid passages in fluid communication with a heat exchanger to control the temperature within the transmission. The manifold is typically configured to include a temperature-sensitive valve arranged to prevent fluid flow through a heat exchanger/radiator until the transmission fluid has warmed up. Prior art flow control valves including wax actuators have used a poppet-type valve and a wax motor to open and close passages in the manifold to direct transmission fluid according to the temperature of the fluid. The valve member typically comprises a planar disc that creates a seal with an annular seat disposed on the manifold cavity between the inlet and outlet pathways. In this actuator configuration, the temperature sensing part of the actuator is positioned in the cavity defined by the manifold and is not exposed directly to fluid flowing from the source of heat. Consequently, the sensitivity and accuracy of prior art actuators of this type can be improved.
Prior art actuators may employ a rubber plug to transmit force from the expanding wax to a piston that provides an actuating movement. This arrangement may absorb some of the force created by expansion of the wax, which may delay actuator response and limit the resulting range of actuator movement. Moreover, prior art valve assemblies may have restricted and/or turbulent fluid flow paths, causing significant pressure drops across prior art valves, thereby reducing the rate of fluid flow through the manifold.
Accordingly, there is a need in the art for an improved, temperature sensitive thermally actuated flow control valve.